Heat pump defrosting unit



Oct. 10,1961 G. L. COAD 3,003,330

HEAT PUMP DEFROSTING UNIT Filed June 26, 1959 (wan-.4502

IN V EN TOR. 65:26! Z. (040 hw m United States Patent 3,003,330 7 HEAT PUMP DEFROSTING UNIT George L. @0211, 3354 Springhill Road, Lafayette, Calif. Filed June 26, 1959, Set. N0. 823,188 2 Claims. (Cl. 62140) This invention relates to and in general has for its obect the provision of frost sensing and control mechanism for heat pumps such as refrigerators, freezers, and air conditioners.

More specifically, one of the objects of this invention is the provision of a defrosting control unit including an expansible chamber having first and second thermal conducting walls insulated from each other, said first wall being provided with a hole of capillary dimensions extending therethrough.

Another object of this invention is the provision in combination with a heat pump of a defrosting control unit of the character above described wherein said hole is located immediately adjacent the cooling unit of said heat pump; wherein the second wall is disposed in spaced, heat exchange relationship with said cooling unit; wherein a heat exchanger is located adjacent said cooling unit; and wherein means is provided responsive to the pressure within said expansible chamber for controlling said heat exchanger.

The invention possesses other advantageous features, some of which, with the foregoing, will be set forth at length in the following description where that form of the invention which has been selected for illustration in the drawings accompanying and forming a part of the present specification is outlined in full. In said drawings, one form of the invention is shown, but it is to be understood that it is not limited to such form, since the invention as set forth in the claims may be embodied in other forms.

Referring to the drawings, the single figure thereof is a diagrammatic illustration of a heat pump embodying the objects of my invention.

For purposes of illustration, the heat pump shown in the drawings is in the form of a refrigerator and generally indicated by the reference numeral 1. Forming the principal and customary elements of the refrigerator 1 is an insulated shell or casing 2, a cooling unit 3, a compressor 4, and a condenser 5, the latter three elements being connected in closed circuit through conduits 6, 7, and 8. Extending transversely across the casing 2 is a partition 9 dividing the casing into upper and lower compartments 11 and 12.

Mounted in the upper compartment 11 is a motor 13 for driving the compressor 4 through a belt 14 and pulley wheel 15. Also mounted within the upper compartment 11 is an electric fan 16 for drawing hot air from the upper compartment.

Associated with the conduit 8 is a valve 17 under the control of a float 18 disposed within the cooling unit.

Connected to the motor 13 through a thermostatic switch 19 disposed within the lower compartment 12 are leads 21 and 22 communicating with a suitable source of voltage 23.

The cooling unit 3 and the coils of the condenser are partly filled with a liquid or gas such as liquid ammonia, sulfur dioxide, or methyl chloride or any other suitable refrigerant.

The refrigerator so far described is of standard and well-known construction and operation, and is merely representative of one form of heat pump.

Mounted at least partially within the lower chamber 12 is an expansible chamber generally designated by the reference numeral 31. Forming the chamber 31 is an intermediate section of thermal conducting tubing 32, terminating and communicating at one end in and with 3,003,330 Patented Oct. 10., 1961 a U tube 33, filled with mercury 34 to a level 35. Connected to the other end of the section of tubing 32, through a thermal insulating sleeve 36, is a closed-ended thermal conducting nipple 37 provided with a hole 38 of capillary dimensions.

The nipple 37 should be so positioned relative to the cooling unit that its hole 38 is immediately adjacent the cooling unit 3 to the end that as soon as frost starts to form on the exposed surfaces of the cooling unit 3, frost will also form on the nipple 37 and immediately close or plug the hole 38. Also important to the operation of this invention is the location of at least a part of the tube section 32 in good heat-exchange relationship to a portion of the cooling unit 3. However, it is preferable here that such part of the tube section 32 be somewhat spaced from the cooling unit.

Disposed in the right-hand leg of the U tube 33 above the level of the mercury 34 is a contact point 41 communicating through a lead 42 with one side of an electric heating coil 43 surrounding a portion of the cooling unit 3. The other side of the heating coil 43 communicates through leads 44 and 45 with a source 46 of voltage.

Mounted within the lower end of the mercury tube 34 is a common contact point 47 communicating through a lead 48 with the source of voltage 46. With the level of the mercury tube 33 standing as shown in full line in the drawing, the electric circuit just described is open, but will be closed it the mercury level rises in the right-hand leg of the mercury tube 33 so as to close on the contact point 41. This will occur upon a decrease in the air pressure within the expansible chamber 31 and this in turn will take place upon a decrease in the temperature of the air within the chamber 31. As mentioned above, the initial deposit of frost on the cooling unit 3 will result in closing or plugging the hole 38. As ice continues to build up on the cooling unit 3, the temperature of the adjacent portion of the metal tubing 32 will drop, thus causing a drop in the temperature of the air within expansible chamber 31. This will, of course, result in a corresponding drop of the pressure within the expansible chamber and permit the mercury to rise in the right-hand side leg of the mercury tube 33 and to close over the contact point 41. The circuit through the heating coil 43 is thereby completed, whereupon the defrosting cycle of the refrigerator is initiated and will continue until such time as the hole 38 is cleared not only of ice but also of water. This is highly desirable, for if the refrigeration cycle is initiated while water is still adhering to the surfaces of the cooling unit 3, such water will immediately (or at least shortly) freeze, together with water disposed over the hole 38. This will result in prematurely initiating the defrosting cycle. This, of course, is undesirable but can be avoided by making the hole 38 of capillary dimensions, for then water in the hole can be removed only by evaporation and maintains the hole closed until the surface water of the cooling unit has likewise been evaporated.

The location of expansible chamber 31 is immaterial so long as the nipple 37 is mounted immediately adjacent a part of the cooling unit 3, and so long as a portion of the tubing section 32 is in heat-exchange relationship with the cooling unit. Although the movable element of the expansible chamber 31 has here been illustrated as the body of mercury 34, a diaphragm or Sylphon could also be made to serve the same or equivalent P p Communicating with the motor 51 of the fan 16 is a lead 52 terminating in a contact point 53 disposed within the mercury tube 33. The other terminal of the motor 51 communicates through the lead 45 with the source of voltage 46. As a result of this arrangement it will be a 3 seen that during the defrosting cycle the fan motor circuit is broken by reason of the fact that the mercury in the left-hand leg of the mercury tube drops below the level of the contact point 53, and that this circuit will be closed only during the non-defrosting cycle of operationof the heat pump. 1

It should also be where noted that the'mereury switch can be used to control the compressor motor 13, and more particularly to open its circuit during the defrosting cycle.

I claim:

1. In combination, a heat pump including a cooling unit in closed fluid circuit with a condenser and a compressor; a control unit comprising: an air chamber mounted immediately adjacent said cooling unit and provided with a capillary opening facing said cooling unit and arranged to be closed upon the formation of ice or 'frost on said cooling unit; a conduit connected at one end to said chamber and having a thermal conducting portion spaced from but in heat exchange relationship with said cooling unit; first means connected'to the other end of said conduit for sensing pressure variations within said conduit; and second means responsive to said first means for controlling the cycle of operation of said heat pump.

2. In combination, a heat pump including a cooling unit in closed fluid circuit with a condenser and a compressor; a control unit comprising: an air chamber mounted immediately adjacent said cooling unit and provided with a capillary opening facing said cooling unit and arranged to be closed upon the formation of ice or frost on said cooling unit; a conduit connected at one end to said chamber and having a thermal conducting portion spaced from but in heat exchange relationship with said cooling unit, said chamber andconduitbeing thermally insulated from each other; first means connected to the other end of said conduit for sensing pressure variations within said conduit; and second means responsive to said first means for controlling the cycle of operation of said heat pump.

References Cited in the file of this patent UNITED STATES PATENTS 1,455,633 Lundgaard a May 15, 1923 1,937,698 Hofiman Dec. 6, 1933 2,722,108 Hailey Nov. 1, 1955 2,724,950 Rothwell' Nov. 29, 1955 2,744,389 Raney May 8, 1956 

